FET coil update

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <cwillis-at-guilford.edu>


Hello SSTC coilers-

Thanks so much for your support on my questions, including the gate drive
transformer issue.  On a tip from Malcolm, I managed to get that part built
right.  I also scrapped my one-transistor design and went to a more
desirable half-bridge configuration, and I have a new controller that uses
a PWM chip and a 555 timer "interrupter."  The coil can let out 9" of spark
max when fed from the 120-V mains, drawing somewhere less than 300 W (don't
know how much other than that.)  The MOSFETs only get lukewarm!

The interrupter function allows some super neat effects.  Depending on duty
cycle and frequency of the interrupter, I can get a crackly hum (emulating
conventional coil operation with short pulses, low duty cycle and thin,
whitish sparks); fat throbbing "swords" like those from a standard tube
coil;  shrieking sheets of beautiful banjo streamers (this is really the
best, though it's hard on the ears) and all kinds of other fun stuff.   I
wish I had a good picture of this happening; unfortunately, my digital
camera isn't up to the task of making good spark shots. 

To see a few photos, go to 
www.angelfire-dot-com/electronic/cwillis/sstc2.html
I think I'll put the schematic up on my website also sometime soon.

As always, your comments / suggestions are greatly appreciated!

-Carl